1. Field of the invention
The present disclosure relates to a mobile terminal, and more particularly, to the location measurement of a mobile terminal.
2. Description of the related art
In recent years, location measurement technologies for checking the location of a mobile terminal in real time have been widely used, and there are provided various location-based services on the basis of the technologies. In order to provide a location-based service, the process of measuring a current location of the terminal should be carried out in advance.
In general, technologies for measuring the location of a mobile terminal may include a GPS-based scheme and a mobile communication system-based scheme.
For the GPS-based scheme, a GPS receiver is incorporated in a mobile terminal to compute a distance between a GPS satellite and the GPS receiver, thereby obtaining a coordinate value thereof.
The mobile communication system-based scheme may include a Time Of Arrival (TOA) measurement method, a Time Difference Of Arrival (TDOA) measurement method, an Angle Of Arrival (AOA) measurement method, and the like.
For the TOA method, a time of radio wave arrival between a mobile terminal and a base station may be measured to measure the location of the mobile terminal.
For the TDOA method, the location of a mobile terminal may be determined by using a time difference between signals transmitted from different places. A radio wave time difference in proportion to a distance difference from two base stations to a mobile terminal may be measured, and the mobile terminal may be located on a position having a constant distance difference from the two base stations, namely, on a hyperbolic curve with foci at the two base stations. Two hyperbolic curves are obtained from three base stations, and an intersection point between the two hyperbolic curves may become the location of the mobile terminal.
For the AOA method, furthermore, the direction of a signal being arrived from a mobile terminal may be measured at two base stations to obtain an angle of direction, and the location of the mobile terminal may be measured by using the angle of direction.
However, for the location measurement method using a GPS receiver, a GPS receiver should be incorporated in a user equipment, and thus its serviceable devices are limited and the location measurement is difficult in a region incapable of receiving satellite signals. Further, it has a drawback that the power consumption of a mobile terminal is large when driving a GPS receiver.
Meanwhile, an estimation method, using a time difference, a receiving direction or an angle of radio wave arrival, has a drawback that the accuracy of location estimation is low due to a path difference in the environment of many multi-paths.